In color television systems generally a radio frequency carrier wave is modulated with an unipolar composite video signal which includes synchronizing signal components, blanking components, picture or luminance components, and chrominance components comprised by a color subcarrier quadrature modulated with two color signals.
It has also been proposed, to digitally code the composite color signal before modulating the carrier wave, because digitally coded signals are less prone to transmission errors than analog signals. At the receiving end, the original analog composite video signal is reconstructed from the transmitted digital signal by decoding and processed in analog manner as well known in the color television receiver art.
My own German patent No. 30 10 938 describes a method of digital coding using code elements formed by a half or a full period of a sine wave.
The known systems for producing and processing the composite video signal at the transmitting and receiving ends are relatively complicated, specifically if measures are to be taken, as in the PAL and SECAM systems for avoiding color errors by phase distortions in the course of the transmission.